1. Field of the Invention
The present invention relates to an image forming apparatus such as a copier or a printer, in particular to an image forming apparatus with an unit detachably attachable to a main body of the apparatus.
2. Related Background Art
Formerly, an electrophotographic image forming apparatus using an electrophotographic image forming process, for example, employed a process cartridge system making an electrophotographic photosensitive body and process means for acting on the electrophotographic photosensitive body into an integrated cartridge and permitting this cartridge to be detachably attachable to the main body of the image forming apparatus. According to this cartridge system, since the maintenance of an apparatus was performable by a user himself, not by a service man, the manipulability could be markedly improved. Thus, this process cartridge system has been widely applied to an electrophotographic image forming apparatus.
Incidentally, the above process cartridge system is a system integrally making charging means or cleaning means, developing means, and an electrophotographic photosensitive body into a cartridge and permitting the cartridge to be detachably attachable to the main body of an electrophotographic image forming apparatus, or integrally making at least one of charging means and cleaning means, developing means, and an electrophotographic photosensitive body into a cartridge and permitting the cartridge to be detachably attachable to the main body of the electrophotographic photosensitive body, or integrally making an electrophotographic photosensitive body and cleaning means into a cartridge and permitting the cartridge to be detachably attachable to the main body of the electrophotographic photosensitive body.
A process cartridge made by unitizing members necessary for image forming like this is put to practical use to facilitate a maintenance operation such as, the replenishment of a developer or the exchange of a photosensitive body in case a developer or a electrophotographic photosensitive body or the like is used up.
Also, for the process cartridge described above, an additional function has been proposed, for example, of mounting a nonvolatile RAM in a process cartridge as a storing medium, storing the amount used at the main body of an image forming apparatus into this nonvolatile RAM and discriminating the usage limit of a process cartridge on the basis of the information to notify a user of the timing of exchange or urging an exchange as disclosed in Japanese Patent Application Laid-Open No. 59-61854, or of storing a quality code in the above nonvolatile RAM at the time of shipping and disabling the image forming operation unless the quality code coincides with that of the main body of an image forming apparatus for the protection of an apparatus as disclosed in Japanese Patent Application Laid-Open No. 6-149051.
And, in a former image forming apparatus, a connector is generally used in the connection between the nonvolatile RAM loaded on a process cartridge and the main body of an image forming apparatus to permit the process cartridge to be detachably attachable to the main body of the image forming apparatus.
The connector is installed with an easy connection elaborated in attaching a process cartridge to the main body of an image forming apparatus, but consideration is required of using high precision components around the connector or of adopting an easily connecting connector shape for the improvement of reliability in the connection.
Also, when a connection fault of the connector occurs in an image forming apparatus communicating to a storing medium loaded on a process cartridge and detecting the presence or absence of a process cartridge, for example, processing is made by mistake with the process cartridge regarded as unloaded even if it is loaded correctly.
And, when the above storing medium or the connector itself is faulty, processing is made with the process cartridge regarded as unloaded and erroneous information is given to an operator even if the connection of the above connector is securely achieved.
Furthermore, with an image forming apparatus in which the detection of an abnormality in storing medium itself is detected, for example, the occurrence of connection fault in the above connector is processed as an abnormal storing medium by mistake even if the storing medium itself is not abnormal. In this case, because of performing various controls on the basis of an erroneous detected result, the image forming apparatus is damaged in operating stability, thus resulting in a decrease in reliability.
Recently, use of a non-contact antenna for information transmission between the main body of the apparatus and the storing medium of a process cartridge is also proposed.
Those using such non-contact type of communicating means have the merit of being easier in the attachment and detachment of a process cartridge than those using a contact-type of connector as mentioned above.
To perform an accurate communication, however, the positional tolerance of an antenna on the process cartridge side to an antenna on the main body of the apparatus side is restricted to some extent. Accordingly, if the position of an antenna on the process cartridge side exceeds this tolerance in attaching the process cartridge to the main body of the apparatus, a problem similar to that of an apparatus using a contact-type connector occurs.
Thus, to improve the reliability of connecting a connector on the process cartridge side to a connector on the main body of the apparatus side when the process cartridge is attached to the main body of the apparatus, the provision of a biasing means for biasing the process cartridge in the connecting direction of a connector after attaching the process cartridge to the main body of the apparatus was proposed already (U.S. Application Ser. No. 08/900,835, now U.S. Pat. No. 5,909,603). According to this proposition, since it is detected whether conduction to storage means can be normally performed or not after the reliability of connection between the connectors by the biasing means is promoted, there is a merit in that a decision on whether a process cartridge is attached or not is accurately discriminable from a decision on whether storage means is abnormal or not.
The present invention is further improved so as to make this discrimination more correct.